我使用的是linux-rt-4.9.28这一版本的内核。板子是我们参照官方的板子画的。
在移植内核的时候，内核启动后一直不断报 [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040) 这样的一个错误。
想请教下，这个错误是由什么问题导致的。
完整的内核启动log如下：
Starting kernel ...
[ 0.000000] Booting Linux on physical CPU 0x0
[ 0.000000] Linux version 4.9.28-rt16-g786e64041b (michael@michael) (gcc version 6.2.1 20161016 (Linaro GCC 6.2-2016.11) ) #7 PREEMPT RT Wed Aug 9 09:40:44 CST 2017
[ 0.000000] CPU: ARMv7 Processor [412fc09a] revision 10 (ARMv7), cr=10c53c7d
[ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
[ 0.000000] OF: fdt:Machine model: TI AM437x GP EVM
[ 0.000000] efi: Getting EFI parameters from FDT:
[ 0.000000] efi: UEFI not found.
[ 0.000000] cma: Reserved 48 MiB at 0xbd000000
[ 0.000000] Memory policy: Data cache writeback
[ 0.000000] CPU: All CPU(s) started in SVC mode.
[ 0.000000] AM437x ES1.2 (neon)
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 260416
[ 0.000000] Kernel command line: console=ttyO0,115200n8 root=PARTUUID=012887bb-02 rw rootfstype=ext3 rootwait
[ 0.000000] PID hash table entries: 4096 (order: 2, 16384 bytes)
[ 0.000000] Dentry cache hash table entries: 131072 (order: 7, 524288 bytes)
[ 0.000000] Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)
[ 0.000000] Memory: 977232K/1048576K available (7168K kernel code, 299K rwdata, 2368K rodata, 1024K init, 317K bss, 22192K reserved, 49152K cma-reserved, 212992K highmem)
[ 0.000000] Virtual kernel memory layout:
[ 0.000000] vector : 0xffff0000 - 0xffff1000 ( 4 kB)
[ 0.000000] fixmap : 0xffc00000 - 0xfff00000 (3072 kB)
[ 0.000000] vmalloc : 0xf0800000 - 0xff800000 ( 240 MB)
[ 0.000000] lowmem : 0xc0000000 - 0xf0000000 ( 768 MB)
[ 0.000000] pkmap : 0xbfe00000 - 0xc0000000 ( 2 MB)
[ 0.000000] modules : 0xbf000000 - 0xbfe00000 ( 14 MB)
[ 0.000000] .text : 0xc0008000 - 0xc0800000 (8160 kB)
[ 0.000000] .init : 0xc0b00000 - 0xc0c00000 (1024 kB)
[ 0.000000] .data : 0xc0c00000 - 0xc0c4ad60 ( 300 kB)
[ 0.000000] .bss : 0xc0c4ad60 - 0xc0c9a2e0 ( 318 kB)
[ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] Preemptible hierarchical RCU implementation.
[ 0.000000] RCU kthread priority: 1.
[ 0.000000] NR_IRQS:16 nr_irqs:16 16
[ 0.000000] L2C: platform modifies aux control register: 0x0e030000 -> 0x3e430000
[ 0.000000] L2C: DT/platform modifies aux control register: 0x0e030000 -> 0x3e430000
[ 0.000000] L2C-310 enabling early BRESP for Cortex-A9
[ 0.000000] OMAP L2C310: ROM does not support power control setting
[ 0.000000] L2C-310 dynamic clock gating disabled, standby mode disabled
[ 0.000000] L2C-310 cache controller enabled, 16 ways, 256 kB
[ 0.000000] L2C-310: CACHE_ID 0x410000c9, AUX_CTRL 0x4e430000
[ 0.000000] OMAP clockevent source: timer2 at 24000000 Hz
[ 0.000070] sched_clock: 32 bits at 24MHz, resolution 41ns, wraps every 89478484971ns
[ 0.000117] clocksource: timer1: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 79635851949 ns
[ 0.000142] OMAP clocksource: timer1 at 24000000 Hz
[ 0.000640] sched_clock: 64 bits at 500MHz, resolution 2ns, wraps every 4398046511103ns
[ 0.000664] clocksource: arm_global_timer: mask: 0xffffffffffffffff max_cycles: 0xe6a171a037, max_idle_ns: 881590485102 ns
[ 0.000737] Switching to timer-based delay loop, resolution 2ns
[ 0.001767] clocksource: 32k_counter: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 58327039986419 ns
[ 0.001782] OMAP clocksource: 32k_counter at 32768 Hz
[ 0.003371] Console: colour dummy device 80x30
[ 0.003779] WARNING: Your 'console=ttyO0' has been replaced by 'ttyS0'
[ 0.003785] This ensures that you still see kernel messages. Please
[ 0.003790] update your kernel commandline.
[ 0.003900] Calibrating delay loop (skipped), value calculated using timer frequency.. 1000.00 BogoMIPS (lpj=5000000)
[ 0.003914] pid_max: default: 32768 minimum: 301
[ 0.004544] Mount-cache hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.004562] Mountpoint-cache hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.011849] CPU: Testing write buffer coherency: ok
[ 0.014860] Setting up static identity map for 0x80100000 - 0x80100060
[ 0.021695] EFI services will not be available.
[ 0.026269] devtmpfs: initialized
[ 0.068384] VFP support v0.3: implementor 41 architecture 3 part 30 variant 9 rev 4
[ 0.070845] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[ 0.071067] futex hash table entries: 256 (order: 1, 8192 bytes)
[ 0.095537] pinctrl core: initialized pinctrl subsystem
[ 0.107038] NET: Registered protocol family 16
[ 0.112446] DMA: preallocated 256 KiB pool for atomic coherent allocations
[ 0.236635] omap_l3_noc 44000000.ocp: L3 debug error: target 8 mod:0 (unclearable)
[ 0.237599] omap_l3_noc 44000000.ocp: L3 application error: target 8 mod:0 (unclearable)
[ 0.248440] omap_gpio 44e07000.gpio: could not find pctldev for node /ocp@44000000/l4_wkup@44c00000/scm@210000/pinmux@800/gpio0_pins, deferring probe
[ 0.255366] OMAP GPIO hardware version 0.1
[ 0.273489] omap_gpio 48322000.gpio: could not find pctldev for node /ocp@44000000/l4_wkup@44c00000/scm@210000/pinmux@800/display_mux_pins, deferring probe
[ 0.284754] omap-gpmc 50000000.gpmc: could not find pctldev for node /ocp@44000000/l4_wkup@44c00000/scm@210000/pinmux@800/nand_flash_x8, deferring probe
[ 0.299379] hw-breakpoint: found 5 (+1 reserved) breakpoint and 1 watchpoint registers.
[ 0.299480] hw-breakpoint: maximum watchpoint size is 4 bytes.
[ 0.337717] edma 49000000.edma: TI EDMA DMA engine driver
[ 0.353402] omap_i2c 44e0b000.i2c: could not find pctldev for node /ocp@44000000/l4_wkup@44c00000/scm@210000/pinmux@800/i2c0_pins, deferring probe
[ 0.353673] omap_i2c 4802a000.i2c: could not find pctldev for node /ocp@44000000/l4_wkup@44c00000/scm@210000/pinmux@800/i2c1_pins, deferring probe
[ 0.354101] media: Linux media interface: v0.10
[ 0.354239] Linux video capture interface: v2.00
[ 0.354347] pps_core: LinuxPPS API ver. 1 registered
[ 0.354364] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giometti@linux.it>
[ 0.354428] PTP clock support registered
[ 0.354570] EDAC MC: Ver: 3.0.0
[ 0.358743] omap-mailbox 480c8000.mailbox: omap mailbox rev 0x400
[ 0.360256] Advanced Linux Sound Architecture Driver Initialized.
[ 0.366038] clocksource: Switched to clocksource arm_global_timer
[ 0.394062] NET: Registered protocol family 2
[ 0.397896] TCP established hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.398252] TCP bind hash table entries: 8192 (order: 5, 196608 bytes)
[ 0.402199] TCP: Hash tables configured (established 8192 bind 8192)
[ 0.403117] UDP hash table entries: 512 (order: 3, 32768 bytes)
[ 0.404026] UDP-Lite hash table entries: 512 (order: 3, 32768 bytes)
[ 0.407642] NET: Registered protocol family 1
[ 0.410751] RPC: Registered named UNIX socket transport module.
[ 0.410835] RPC: Registered udp transport module.
[ 0.410847] RPC: Registered tcp transport module.
[ 0.410856] RPC: Registered tcp NFSv4.1 backchannel transport module.
[ 0.422619] workingset: timestamp_bits=14 max_order=18 bucket_order=4
[ 0.435397] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[ 0.439219] NFS: Registering the id_resolver key type
[ 0.439422] Key type id_resolver registered
[ 0.439439] Key type id_legacy registered
[ 0.439649] ntfs: driver 2.1.32 [Flags: R/O].
[ 0.447382] bounce: pool size: 64 pages
[ 0.448397] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 247)
[ 0.448455] io scheduler noop registered
[ 0.448467] io scheduler deadline registered
[ 0.448752] io scheduler cfq registered (default)
[ 0.460833] pinctrl-single 44e10800.pinmux: please update dts to use #pinctrl-cells = <1>
[ 0.463471] pinctrl-single 44e10800.pinmux: 199 pins at pa f9e10800 size 796
[ 0.475623] backlight supply power not found, using dummy regulator
[ 0.617563] Serial: 8250/16550 driver, 10 ports, IRQ sharing disabled
[ 0.626955] omap8250 44e09000.serial: No clock speed specified: using default: 48000000
[ 0.631235] 44e09000.serial: ttyS0 at MMIO 0x44e09000 (irq = 30, base_baud = 3000000) is a 8250
[ 1.370226] console [ttyS0] enabled
[ 1.376279] omap8250 481a6000.serial: No clock speed specified: using default: 48000000
[ 1.388665] 481a6000.serial: ttyS3 at MMIO 0x481a6000 (irq = 31, base_baud = 3000000) is a 8250
[ 1.405050] omap_rng 48310000.rng: OMAP Random Number Generator ver. 20
[ 1.413250] [drm] Initialized
[ 1.420675] 4832a000.dss supply vdda_video not found, using dummy regulator
[ 1.428726] OMAP DSS rev 2.0
[ 1.432524] omapdss_dss 4832a000.dss: bound 4832a400.dispc (ops dispc_component_ops)
[ 1.500912] brd: module loaded
[ 1.532818] loop: module loaded
[ 1.546712] libphy: Fixed MDIO Bus: probed
[ 1.626521] davinci_mdio 4a101000.mdio: davinci mdio revision 1.6
[ 1.632785] davinci_mdio 4a101000.mdio: detected phy mask fffffffe
[ 1.642829] libphy: 4a101000.mdio: probed
[ 1.647492] davinci_mdio 4a101000.mdio: phy[0]: device 4a101000.mdio:00, driver Atheros 8031 ethernet
[ 1.660573] cpsw 4a100000.ethernet: Detected MACID = 68:9e:19:b9:d7:20
[ 1.668443] cpsw 4a100000.ethernet: cpts: overflow check period 500 (jiffies)
[ 1.683639] mousedev: PS/2 mouse device common for all mice
[ 1.691768] i2c /dev entries driver
[ 1.785728] NET: Registered protocol family 10
[ 1.798291] sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
[ 1.807868] NET: Registered protocol family 17
[ 1.814119] Key type dns_resolver registered
[ 1.820054] omap_voltage_late_init: Voltage driver support not added
[ 1.867605] GPIO line 119 (SelEMMCorNAND) hogged as output/low
[ 1.883477] GPIO line 136 (SelLCDorHDMI) hogged as output/high
[ 1.897128] omap-gpmc 50000000.gpmc: GPMC revision 6.0
[ 1.902417] gpmc_mem_init: disabling cs 0 mapped at 0x0-0x1000000
[ 1.916536] nand: No NAND device found
[ 1.920408] omap2-nand 8000000.nand: scan failed, may be bus-width mismatch
[ 1.991113] omap_i2c 44e0b000.i2c: bus 0 rev0.12 at 100 kHz
[ 2.004081] omap_i2c 4802a000.i2c: bus 1 rev0.12 at 100 kHz
[ 2.012541] display supply vcc not found, using dummy regulator
[ 2.022565] omap_hsmmc 48060000.mmc: Got CD GPIO
[ 2.089707] omapdrm omapdrm.0: DMM not available, disable DMM support
[ 2.103855] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 2.110730] [drm] No driver support for vblank timestamp query.
[ 2.154841] mmc1: host does not support reading read-only switch, assuming write-enable
[ 2.156942] mmc1: new high speed SDHC card at address 1234
[ 2.161153] mmcblk1: mmc1:1234 SA08G 7.29 GiB
[ 2.168827] mmcblk1: p1 p2
[ 2.185015] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185090] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185116] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185146] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185162] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185191] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185207] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185218] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185233] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185242] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 2.185516] random: fast init done
[ 2.231105] random: crng init done
[ 2.245500] Console: switching to colour frame buffer device 100x37
[ 2.411861] omapdrm omapdrm.0: fb0: omapdrm frame buffer device
[ 2.448991] hctosys: unable to open rtc device (rtc0)
[ 2.469350] vmmcwl_fixed: disabling
[ 2.484900] ALSA device list:
[ 2.487912] No soundcards found.
[ 2.547330] EXT4-fs (mmcblk1p2): mounting ext3 file system using the ext4 subsystem
[ 5.540647] EXT4-fs (mmcblk1p2): warning: mounting fs with errors, running e2fsck is recommended
[ 5.582238] EXT4-fs (mmcblk1p2): recovery complete
[ 5.605762] EXT4-fs (mmcblk1p2): mounted filesystem with ordered data mode. Opts: (null)
[ 5.623203] VFS: Mounted root (ext3 filesystem) on device 179:2.
[ 5.684658] devtmpfs: mounted
[ 5.724422] Freeing unused kernel memory: 1024K (c0b00000 - c0c00000)
mount: mounting none on /dev/pts failed: No such file or directory
mount: mounting tmpfs on /dev/shm failed: No such file or directory
mount: mounting proc on /proc failed: Device or resource busy
[ 7.186117] omap_irq_fifo_underflow: 625350 callbacks suppressed
[ 7.186382] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 7.200092] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 7.207996] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 7.215257] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 7.222663] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 7.229884] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 7.237092] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 7.244409] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 7.251615] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 7.258824] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.124245] net eth0: initializing cpsw version 1.15 (0)
[ 12.196269] omap_irq_fifo_underflow: 1359412 callbacks suppressed
[ 12.196581] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.196634] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.196653] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.196671] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.196692] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.196700] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.196720] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.196730] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.196745] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.196757] [drm:omap_irq_handler] *ERROR* FIFO underflow on gfx (0x00000040)
[ 12.612699] net eth0: initialized cpsw ale version 1.4
[ 12.617888] net eth0: ALE Table size 1024
[ 12.733563] Atheros 8031 ethernet 4a101000.mdio:00: attached PHY driver [Atheros 8031 ethernet] (mii_bus:phy_addr=4a101000.mdio:00, irq=-1)
[ 12.813494] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
